In dentistry, the restoration of a patient's tooth or teeth generally includes the replacement of the natural tooth substance by an artificial substance. For larger restorations, pre-finished dental restorations or prostheses are commonly used to replace at least a part of the tooth or teeth.
In recent years ceramic and glass-ceramic materials have been widely used for making such dental restorations, because of their good physical, aesthetic and biocompatible properties. These restorations are often manufactured by an automated process, which typically includes:                capturing the shape of a patient's teeth, for example by scanning;        designing the shape of the dental restoration using computer-aided design (CAD) software; and        manufacturing the dental restoration by an automated Computer Numerical Controlled (CNC) machine.        
One common method of making dental restorations is based on providing a standardized blank of ceramic, glass-ceramic or glass material and machining the dental restoration from that blank by material removal. Some methods are further based on the use of blanks made of a pre-sintered material. Such pre-sintered material is typically provided by compacting ceramic/glass-ceramic particles to a blank which is subsequently fired or pre-sintered so that the particles cohere sufficiently to provide the blank with a certain mechanical stability and so that the blank still has an open-celled structure due to voids still present between adjacent particles. A so formed blank has a lower mechanical strength than the ceramic/glass-ceramic material from which it is made, and accordingly, such a blank can be machined relatively easily. The dental restoration can be obtained from such a blank by machining an oversized precursor of the dental restoration from that blank. This dental restoration precursor is typically fired or sintered until substantially all voids are eliminated to form the dental restoration. Due to the elimination of the voids the material shrinks during sintering so that the originally oversized dental restoration precursor converts into the appropriately sized dental restoration.
One technical challenge is the coloring of dental restorations to the desired tooth color. While there are advantages of using standardized blanks during manufacturing, it is generally desirable to provide a dental restoration at a color or color structure which resembles the color structure of a natural tooth. There have been attempts to color pre-sintered precursors of dental restorations with so-called dental coloring solutions.
Commercially available dental coloring solutions typically comprise water, metal cations selected from rare earth elements, transition metal and mixtures thereof, optionally complexing agent(s) and/or further additives like (poly)ethylene glycol. The coloring solutions are typically used for homogeneously coloring of porous dental ceramics. The coloring solutions are applied to the dental ceramic being in a porous and absorbent stage. After sintering, the dental ceramic usually shows a tooth-like color and can be directly used as a monolithic restoration or is ready for applying an additional veneering layer.
A dental restoration precursor can for example be immersed in such a dental coloring solution before it is sintered and thus may be provided with a desired tooth color. Further there have been attempts to provide different portions of the dental restoration with different colors, for example by applying different coloring solutions to different areas of the dental restoration precursor using a brush.
WO 2013/029791 A1 discloses a brush for applying a coloring solution to ceramics in the dental area. The brush comprises a brush tip, a connecting piece and a gripping piece. The gripping piece comprises a reservoir for receiving a color liquid and the connecting piece comprises a liquid depot.
While existing methods and tools for making dental restorations in desired individual colors provide certain advantages there is still a need for a method and device which are easy to use, relatively inexpensive and which allow the making of high quality dental restorations.